Method of manufacturing stamper

ABSTRACT

According to one embodiment, a method of manufacturing a stamper used for manufacturing a magnetic recording medium having magnetic patterns corresponding to servo areas including a preamble section, an address section and a burst section and data areas including discrete tracks, the method includes forming additional resist patterns such that protrusions and recesses appear alternately in the radial direction in the preamble section and/or address section, in forming resist patterns corresponding to the servo areas including the preamble section, the address section and the burst section and data areas including discrete tracks are formed on a master plate, depositing a conductive film on the entire surface of the master plate and resist patterns, followed by electroforming a metal layer, and peeling off the metal layer from the master plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2008-163775, filed Jun. 23, 2008, the entire contents of which are incorporated herein by reference.

BACKGROUND

1. Field

One embodiment of the present invention relates to a method of manufacturing a stamper used for manufacturing of magnetic recording media such as discrete track recording media.

2. Description of the Related Art

In order to improve the recording density of a magnetic recording medium, it is effective to use a discrete track recording medium in which a part of a magnetic recording layer is removed or modified to form recording tracks and separating regions thereby reducing interference between adjacent tracks relating to read and write.

An example of a method of manufacturing a discrete track recording medium by imprinting using a stamper will be described with reference to FIGS. 7A to 7F.

An underlayer 52 and a magnetic recording layer 53 are formed on a substrate 51. A resist 61 is applied to the magnetic recording layer 53 (FIG. 7A). A stamper 40 on which patterns of protrusions and recesses are formed is disposed opposite to the resist 61. Then, imprinting is performed to transfer the patterns of protrusions and recesses of the stamper 40 to the resist 61 by imprinting (FIG. 7B). After the stamper 40 is removed, resist residues remaining in the recesses are removed. Then, the magnetic recording layer 53 is etched using the patterns of the remaining resist 61 as masks to form magnetic patterns 53 a (FIG. 7C). The patterns of the resist 61 are stripped off (FIG. 7D). A nonmagnetic layer 54 is deposited on the entire surface to fill the recesses between the magnetic patterns 53 a with the nonmagnetic layer 54 (FIG. 7E). The nonmagnetic layer 54 on the surface is etched back until the magnetic patterns 53 a are exposed to flatten the surface (FIG. 7F).

An example of the method of manufacturing a stamper used for the aforementioned imprinting will be described with reference to FIGS. 8A to 8F.

A Si wafer 31 is prepared and a resist 32 is applied to the Si wafer 31 (FIG. 8A). The resist 32 is subjected to electron-beam lithography in according with predetermined patterns (FIG. 8B). The resist 32 is developed by removing the unhardened portions to form resist patterns 32 a. The resultant structure is used as a master plate 35 (FIG. 8C). A Ni conductive film 36 is deposited on the entire surface of the master plate 35 using a sputtering apparatus (FIG. 8D). A Ni electroforming film 37 is deposited on the Ni conductive film 36 by electroforming (FIG. 8E). The resultant Ni electroforming film 37 is peeled off from the master plate (FIG. 8F). The Ni electroforming film 37 is washed to manufacture a stamper 40.

In the case of manufacturing a son stamper, for example, a father stamper is used as the master plate and the steps of FIGS. 8D to 8G are carried out.

As stampers capable of forming patterns of protrusions and recesses on a magnetic recording medium with high precision, those disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication Nos. 2007-149196 and 2007-141280 are known. Such a stamper has protrusions different in height. When the protrusions of the stamper are pressed uniformly to a resist, the resist residues are formed with a uniform thickness, thereby forming patterns of protrusions and recesses on the magnetic recording medium with high precision.

However, in manufacturing the stamper, another problem is posed. Specifically, in manufacturing a nickel stamper to which the patterns of protrusions and recesses of the master plate are transferred is produced by electroforming in the above manner, deviation in the transferred positions of the patterns of protrusions and recesses may be produced. As a result, this gives rise to a problem of increase in repeatable runout (RRO) of the discrete track recording medium. The above Jpn. Pat. Appln. KOKAI Publication Nos. 2007-149196 and 2007-141280 do not take the problem into consideration.

The problem of RRO will be described in more detail with reference to the drawings.

FIG. 9A shows the state of the stamper 40 formed by depositing nickel on the master plate 35 by electroforming. In this state, compressive strain is produced in the stamper 40 made of the Ni electroforming film. Thus, when the master plate 35 (FIG. 9B) is separated from the stamper 40 (FIG. 9C), the outer diameter b of the patterned part of the stamper 40 is made smaller by 0.01 to 0.05% than the outer diameter a of the patterned part of the master plate 35.

At this time, if the patterned part of the stamper 40 is evenly contracted, no problem is imposed. Because the degree of contraction is different depending on the position of the stamper 40, however, such a phenomenon occurs that the recording track does not form a true circle. This phenomenon is observed based on that the RRO value is increased. This phenomenon is referred to as transfer defects.

One of the reasons why the degree of contraction is different depending on the position of the stamper 40 is that the amount of deformation of the resist pattern during electroforming differs depending on the density of the resist pattern existing on the master plate 35, as will be described below.

FIG. 10 shows a plan view of the master plate. Data areas 1 (track areas) and servo areas 2 are formed on the master plate 35. Although FIG. 10 shows that 15 servo sectors exist on the master plate 35, 100 or more servo sectors actually exist. In FIG. 10, the area obtained by dividing the circumference of the master plate 35 by the number of the servo areas 2, in which the servo area is set at the center, is called a “division” for the sake of convenience.

FIG. 11 shows a plan view of an example of resist patterns formed on a conventional master plate. FIG. 11 is an enlarged view of the A part in FIG. 10, for example. The hatched parts are resist patterns forming protrusions. As shown in FIG. 11, a servo area 2 is sandwiched between two data areas (track areas) in the circumferential direction (x direction). The serve area 2 includes a preamble section 21, an address section 22 and a burst section 23. In the preamble section 21, resist patterns forming long protrusions extending in the radial direction and recesses appear alternately in the circumferential direction. In the burst section 23, dot-like recesses arranged in the circumferential direction and radial direction are surrounded by a resist pattern forming protrusions. In the address section 22, the shape of the resist patterns differs in each address. In the data area (track area) 1, resist patterns forming long protrusions extending in the circumferential direction and recesses appear alternately in the radial direction.

The behavior of the resist pattern 32 a of the preamble section 21 and Ni electroforming film 36 during electroforming will be described with reference to FIGS. 12A and 12B. FIGS. 12A and 12B show a section in the radial direction where the center axis is shown on the left. The resist pattern 32 a of the preamble section 21 shown in FIG. 12A is formed with a length L of 12 mm (12000000 nm) and a height H of 80 nm. Since compressive strain is produced during electroforming as described above, force towards the center acts on the resist depending on the amount of deposited nickel by electroforming. The resist pattern 32 a receives the compressive stress applied to the Ni electroforming film only on the side wall on the outer peripheral side. When the thickness of the Ni electroforming film 36 is more thickened, the compressive stress increases and exceeds the shearing yield stress of the resist pattern 32 a. Because the resist pattern 32 a of the preamble section 21 is a very long rectangular parallelepiped, the whole resist pattern 32 a never translate in parallel. As shown in FIG. 12B, the resist pattern 32 a will be easily deformed along the shear plane from the side wall of outer peripheral side.

The behavior of the resist pattern 32 a in the data area (track area) 1 and Ni electroforming film 36 during electroforming will be described with reference to FIG. 13. In the data area (track area) 1, resist patterns forming a long protrusions extending in a circumferential direction and recesses appear alternately in the radial direction. As shown in FIG. 13, the side wall of the resist pattern 32 a appears periodically at an interval of track pitch from the outer peripheral side to the inner peripheral side in the radial direction. Thus, the compressive stress produced in the Ni electroforming film 36 is dispersed. However, the stress applied to the side wall of each resist pattern 32 a is not uniform but is larger on the outer peripheral side. Since the compressive stress is dispersed in the data area (track area) 1 as described above, the resist pattern 32 a is more resistant to deformation than in the preamble section 21. However, the resist pattern 32 a is deformed depending on the situation even in the data area (track area) 1.

It is found from the comparison between FIGS. 12 and 13 that the ability of withstanding the compressive stress of the Ni electroforming film 36 is increased with increase in the number of resist patterns 32 a in the radial direction. As shown in FIG. 11, since the address is noted by a binary number in the address section 22, the number of protrusions of the resist patterns 32 a in the radial direction is reduced with increase in digit number. The number of protrusions of the resist patterns 32 a in the address section 22 is closer to that in the preamble section 21 compared to that in the track section 1. It is therefore considered that the resist pattern in the address section 22 shows the same behavior as that in the preamble section 21. As shown in FIG. 11, the burst section 23 has a structure close to that of the track section 1 and it is considered that the resist pattern in the burst section 23 has the same behavior as that in the track section 1.

The mechanism of the generation of RRO will be described with reference to FIG. 14. Compressive stress is produced in the Ni electroforming film in electroforming, so that the Ni electroforming film tends to contract. In the track section 1 and the burst section 23, the compressive stress of the Ni electroforming film is dispersed by the side walls of many resist patterns as shown in FIG. 13 and thus, the resist pattern 32 a is resistant to deformation. In the preamble section 21 and address section 22, on the other hand, the resist pattern is deformed by the compressive stress of the Ni electroforming film and tends to move towards the center. Because the Ni electroforming film deposited by electroforming is a continuous film, the deformation in the preamble section 21 and address section 22 influences on the track section 1 and burst section 23. As a result, the locus of a one-round track which is essentially expected to form a true circle is deformed towards the center in a part of one division. Thus, RRO is produced.

As described above, the compressive stress of the Ni electroforming film is dispersed in many resist patterns in the track section 1. If the dispersed compressive stress is sufficiently high, the resist pattern is also deformed in the track section 1. Because the compressive stress of the Ni electroforming film is larger on the outer peripheral side, the deformation of the resist pattern in the track section 1 arises from the outer peripheral side. When, as shown in FIG. 15, the deformation of the resist pattern arises in the track section 1 and burst section 23 together with the deformation of the resist pattern in the preamble section 21 and address section 22, the locus of a one-round track is deformed towards the center in the division in a wide range.

Also, the arrangement of the resist pattern formed in the address section 22 differs depending on the position on the address, i.e., on the master plate. Thus, the amount of deformation of the resist pattern is different in the address sections 22 at different positions. Therefore, as shown in FIG. 16, the amount of deformation of the resist pattern is different in each division, and there is the case where the locus of one-round track is deformed towards the center in various amounts of deformation in each division. FIG. 16 shows the case where the master plate is divided into eight divisions, for the sake of convenience.

As described above, the conventional method of manufacturing a stamper used for manufacturing a discrete track recording medium has a problem that a large RRO is produced.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A general architecture that implements the various feature of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.

FIGS. 1A and 1B are plan views showing resist patterns in a conventional preamble section and resist patterns in a preamble section in Example 1;

FIGS. 2A and 2B are plan views showing resist patterns in a conventional address section and resist patterns in an address section in Example 2;

FIG. 3 is a plan view showing resist patterns in a preamble section in Example 3;

FIGS. 4A to 4C are plan views showing resist patterns in a conventional address section, resist patterns constituting a Hamming code and resist patterns in an address section in Example 4;

FIG. 5 is a plan view showing resist patterns on a master plate in Example 5;

FIG. 6 is a block diagram showing a magnetic recording apparatus according to the present invention;

FIGS. 7A to 7F are cross-sectional views showing a method of manufacturing a discrete track recording medium;

FIGS. 8A to 8G are cross-sectional views showing a method of manufacturing a stamper;

FIGS. 9A to 9C are perspective views showing a master plate and a stamper;

FIG. 10 is a plan view of a master plate;

FIG. 11 is a plan view showing an example of resist patterns formed on a conventional master plate;

FIGS. 12A and 12B are cross-sectional views for describing the behavior of a resist pattern and Ni electroforming film in a preamble section during electroforming;

FIG. 13 is a cross-sectional view for describing the behavior of a resist pattern and Ni electroforming film in a data area during electroforming;

FIG. 14 is a view for describing the mechanism of generation of RRO;

FIG. 15 is a view for describing the mechanism of generation of RRO; and

FIG. 16 is a view for describing the mechanism of generation of RRO.

DETAILED DESCRIPTION

Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment of the invention, there is provided a method of manufacturing a stamper used for manufacturing a magnetic recording medium having magnetic patterns corresponding to servo areas including a preamble section, an address section and a burst section and data areas including discrete tracks, the method comprising: forming additional resist patterns such that protrusions and recesses appear alternately in the radial direction in the preamble section and/or address section, in forming resist patterns corresponding to the servo areas including the preamble section, the address section and the burst section and data areas including discrete tracks are formed on a master plate; depositing a conductive film on the entire surface of the master plate and resist patterns, followed by electroforming a metal layer; and peeling off the metal layer from the master plate.

FIG. 10 shows a plan view of a master plate. Data areas 1 (track areas) and servo areas 2 are formed on a master plate 35. The data areas 1 (track areas) and the servo areas 2 correspond to areas to be formed on a discrete track recording (DTR) medium to be manufactured. Although FIG. 10 shows that 15 servo sectors exist on the master plate 35, 100 or more servo sectors actually exist.

The data areas of a DTR medium are areas used for recording user data. The data area has a structure in which recording tracks extending in the circumferential direction are formed periodically at a constant track pitch T_(p) with separating regions sandwiched therebetween in the radial direction.

The servo areas of the DTR medium are areas where magnetic patterns corresponding to the information for head positioning are formed. The servo areas on the medium have a circular arc shape along the locus of the head of the magnetic recording apparatus in the access operation. The length in the circumference direction of the servo area is made longer in proportion to the radius value from the center.

In the DTR medium, as shown in, for example, FIG. 7F, a nonmagnetic layer 54 is filled in recesses between the magnetic patterns 53 a to form separating regions. A thin magnetic recording layer may be left in the separating region. Also, the separating regions may be formed by modifying the characteristics such as crystallinity of the magnetic recording layer between the magnetic patterns 53 a. When recesses exist between the magnetic patterns 53 a as described above, it is preferable to fill the recesses with a nonmagnetic layer to flatten the surface of the medium.

The resist patterns formed on a conventional master plate will be described again with reference to FIG. 11 for the sake of convenience. As shown in FIG. 11, a servo area 2 is sandwiched between two data areas (track areas) 1 in the circumferential direction (x direction). The servo area 2 includes a preamble section 21, an address section 22 and a burst section 23. In the preamble section 21, resist patterns forming long protrusions extending in the radial direction and recesses appear alternately in the circumferential direction. In the burst section 23, dot-like recesses arranged in the circumferential direction and radial direction are surrounded by a resist pattern forming protrusions. In the address section 22, the shape of the resist patterns differs in each address. In the data area (track area) 1, resist patterns forming long protrusions extending in the circumferential direction and recesses appear alternately in the radial direction.

Functions of the preamble section, address section and burst section in the DTR medium will be described.

The preamble section is provided for performing PLL processing for synchronizing a servo signal read clock with respect to the time lag occurring due to the rotational deviation of the medium and AGC processing for properly maintaining signal read amplitude.

The address section has a servo signal recognition code called a servo mark, sector data, and cylinder data, which are formed in Manchester codes at the same pitch as the circumferential pitch of the preamble section. Since the cylinder data is formed as patterns the data of which changes every servo track, it is converted into Gray codes, in which change of the code from the adjacent track is made minimum, and then is recorded in Manchester codes so that influence of address read error in seek operation can be reduced. In the figure, the Manchester codes are omitted for the sake of convenience.

The burst section is an off-track detection region for detecting the off-track amount from the cylinder address in the on-track state, where four types of marks (called A, B, C, and D bursts) having shifted pattern phases in the radial direction are formed. In each of the A, B, C and D bursts, marks are arranged in the circumferential direction at the same pitch as that in the preamble section. The cycle of each burst in the radial direction is in proportion to the cycle of change in the address pattern, in other words, the servo track cycle. The shape of the marks in the burst section is designed so as to have a rectangular shape, or, in a strict sense, a parallelogram shape in consideration of the skew angle in the head access. However, the marks are formed in a somewhat rounded shape depending on processing accuracy of a stamper and processing performance in transferring. The marks are formed as the non-recording regions. Average amplitude values of read signals from the A, B, C and D bursts are processed to calculate the off-track amount.

Preferred examples of resist patterns on the master plate for manufacturing the stamper used in manufacturing of a DTR medium as described above will be described. Conventional resist patterns will be shown as needed in the following descriptions to compare with the resist patterns of the present invention.

EXAMPLE 1

FIG. 1A shows resist patterns in a conventional preamble section and FIG. 1B shows resist patterns in a preamble section in this example.

As shown in FIG. 1B, the preamble section in this example is prepared by inserting a string of redundant bits 212 between resist patterns 211 in a conventional preamble section. In this example, one string of redundant bits 212 is inserted between every two strings of resist patterns 211. In the string of redundant bits 212, the bits are changed to be 1010 in the radial direction.

The resist pattern 211 in the conventional preamble section has a long shape extending in the radial direction and is easily deformed when the compressive stress produced in the Ni electroforming film during electroforming is applied thereto. In a string of redundant bits 212, on the other hand, since the bits are arranged to be 1010 in the radial direction, the compressive stress produced in the Ni electroforming film during electroforming can be dispersed and thus the resist patterns are resistant to deformation. Therefore, insertion of the string of redundant bits 212 between the resist patterns 211 makes it possible to suppress the deformation of the resist patterns in the whole preamble section, with the result that RRO of the DTR medium finally manufactured can be reduced.

EXAMPLE 2

FIG. 2A shows resist patterns in a conventional address section and FIG. 2B shows resist patterns in the address section in this example.

The resist patterns 221 of the address section shown in FIG. 2A are formed using Gray codes. As shown in FIG. 2B, the address section in this Example is obtained by inserting a string of redundant bits 222 between the resist patterns 221 of the conventional address section. In this example, one array of redundant bits 222 is inserted every one array of resist patterns 221. In the array of redundant bits 212, the bits are changed to be 1010 in the radial direction.

In this example, insertion of a string of redundant bits 222 between the resist patterns 221 makes it possible to suppress the deformation of the resist patterns in the whole address section, with the result that RRO of the DTR medium finally manufactured can be reduced.

EXAMPLE 3

FIG. 3 shows resist patterns in the preamble section in this example. The resist patterns 211 a in the preamble section in this example are separated by recesses in the radial direction, which are formed in the same manner as those in the track areas 1.

Formation of the resist patterns 211 a separated by recesses in the radial direction makes it possible to suppress the deformation of the resist patterns in the whole preamble section, with the result that RRO of a DTR medium finally manufactured can be reduced.

EXAMPLE 4

FIG. 4A shows resist patterns in a conventional address section, FIG. 4B shows resist patterns constituting a Hamming code as an error correcting code and FIG. 4C shows resist patterns in the address section in this example.

Bit strings 223 of Hamming code shown in FIG. 4B are generated from Gray codes. Here, Hamming codes for an address noted by 6 bits will be described. The number of bits required for a Hamming code is 5. The bit strings of Hamming codes are represented by P1, P2, P3, P4 and P5. At this time, each bit string is determined as follows.

The bit string P5 is determined such that the number of is is made an odd number when the bits 1, 2, 3, 4 and 5 and the P5 bit are added. If the bits 1, 2, 3, 4 and 5 are 00110, P5 is set to 1, so that the number of is is an add number. If the bits 1, 2, 3, 4 and 5 are 10101, P5 is set to 0, so that the number of is is an add number. The bit string P4 is determined based on the bits 1, 2, 3, 4 and 6. The bit string P3 is determined based on the bits 1, 2, 3, 5 and 6. The bit string P2 is determined based on the bits 1, 2, 4, 5 and 6. The bit string P1 is determined based on the bits 1, 3, 4, 5 and 6. When the bit strings 223 of Hamming codes are viewed in the radial direction, there is a place where 11 are arranged and a place where 00 are arranged, showing that the arrangement of the bits is not necessarily 1010 unlike in Examples 1 and 2. However, because almost all parts have an arrangement of 1010, even the bit strings 223 of Hamming codes ensure such an effect that the compressive stress produced in the Ni electroforming film during electroforming is dispersed to provide resistance to deformation.

As shown in FIG. 4C, the address section in this example is obtained by inserting Hamming code-like bit strings between the resist patterns 221 in the conventional address section. In this case, the whole parity bit strings P is inserted between the bits 1 and 2. In the case of inserting the bit strings 223 of Hamming codes in this manner, the compressive stress produced in the Ni electroforming film during electroforming can be dispersed and the resist patterns are therefore scarcely deformed.

EXAMPLE 5

FIG. 5 shows resist patterns on a master plate in this example. This master plate has resist patterns 250 formed so as to extend in the circumferential direction and to be separated from each other in the radial direction in a region positioned on the outside of the outer periphery of the magnetic recording medium, the resist patterns having shapes similar to those of discrete tracks.

The deformation of the resist patterns on a master plate during electroforming tends to arise from the outer peripheral side. Actually, it is known that RRO is larger on the outer peripheral side of the medium. In other words, transfer defects tend to be concentrated on the outer peripheral side. Since the resist patterns 250 having shapes similar to discrete tracks are formed in the region positioned on the outside of the outer periphery of the magnetic recording medium, the deformation of resist patterns can be suppressed on the whole surface of the master plate and RRO of the DTR medium finally manufactured can be reduced. If the Ni electroforming film is peeled off from the master plate after electroforming and then the region positioned on the outside of the outer periphery of the magnetic recording medium is removed, the transfer defects in the region used for the manufacturing of a stamper will be reduced.

When many resist patterns are formed in the region positioned on the outside of the outer periphery of the magnetic recording medium by EB lithography, these patterns may be made in spiral patterns to shorten the time for EB lithography.

As described above, the deformation of resist patterns during electroforming can be suppressed by forming additional resist patterns such that protrusions and recesses appear alternately in the radial direction in the preamble section and/or address section. As a result, RRO caused by transfer defects on a discrete track recording medium can be reduced.

The stamper according to the present invention may be manufactured using the same method described with reference to FIGS. 8A to 8G except that electron beam lithography is controlled so as to form resist patterns shown in each example.

In the manufacturing of a DTR medium using the stamper according to the present invention, the method described with reference to, for example, FIGS. 7A to 7F may be used.

Next, materials and steps preferably used in the manufacturing of the DTR medium will be described.

Examples of the material of the substrate include a glass substrate, Al-based alloy substrate, ceramic substrate, carbon substrate, Si-single crystal substrate having an oxide surface and those prepared by plating these substrates with NiP or the like.

As the soft magnetic underlayer, materials including Fe, Ni or Co are used. Specific examples of these materials include FeCo-based alloys such as FeCo and FeCoV, FeNi-based alloys such as FeNi, FeNiMo, FeNiCr and FeNiSi, FeAl-based alloys and FeSi-based alloys such as FeAl, FeAlSi, FeAlSiCr, FeAlSiTiRu and FeAlO, FeTa-based alloys such as FeTa, FeTaC and FeTaN and FeZr-based alloys such as FeZrN.

As the magnetic recording layer, a ferromagnetic material made of CoCrPt—SiO₂ is typically used.

The resist is used as a mask for processing the magnetic recording layer after patterns of protrusions and recesses are transferred by imprinting. The resist material may be any material as long as it enables the transfer of patterns of protrusions and recesses by imprinting after coating and includes a polymer material, low-molecular organic material and liquid Si resist. Examples of the liquid Si resist include SOG (spin-on glass).

The nonmagnetic material to be filled in the recesses between the magnetic patterns is not particularly limited as long as it is not a ferromagnetic material, and include carbon, oxides such as SiO₂ and A1 ₂ 0 ₃ and metals such as Ti, Cr, Ni, Mo, Ta, Al and Ru, and alloys and compounds of these metals.

The transfer step shown in FIG. 7B is carried out by imprint lithography using a dual-sided transfer type imprinting apparatus. A resist (for example, SOG) is applied on both sides of a disk substrate for perpendicular recording, and imprint stampers having desired patterns of protrusions and recesses are arranged on both sides and pressed under a uniform pressure from both sides to transfer the patterns of protrusions and recesses to the resist.

In FIG. 7C, the resist residues left in the recesses are removed to expose the surface of the magnetic recording layer 53. As a result, protruded resist patterns are formed on the positions where magnetic pattern are to be formed. The magnetic recording layer 53 is subjected to ion milling using the remaining resist patterns as masks to form magnetic patterns 53 a.

In FIG. 7D, remaining resist patterns are removed by etching. In FIG. 7E, a nonmagnetic layer 54 is formed on the entire surface to fill the nonmagnetic layer 54 in the recesses between the magnetic patterns 53 a. In FIG. 7F, the nonmagnetic layer 54 on the surface is etched back until the magnetic patterns 53 a are exposed to flatten the surface. Further, the surface is polished, a DLC protective layer is formed, and then a lubricant is applied to manufacture a DTR medium.

Next, a magnetic recording apparatus having the magnetic recording medium according to the present invention will be described. FIG. 6 shows a block diagram of the magnetic recording apparatus according to the present invention. The figure shows a head slider only over a top side of the magnetic recording medium. However, a perpendicular magnetic recording layer having discrete tracks is formed on both sides of the magnetic recording medium. A down head and an up head are provided over the top side and under the bottom side of the magnetic recording medium, respectively. The configuration of the magnetic recording apparatus according to the present invention is basically similar to that of the conventional magnetic recording apparatus except that the DTR medium according to the present invention is used.

A disk drive includes a main body portion called a head disk assembly (HDA) 100 and a printed circuit board (PCB) 200.

The head disk assembly (HDA) 100 has a DTR medium 55, a spindle motor 101 that rotates the DTR medium 55, an actuator arm 103 that moves around a pivot 102, a suspension 104 attached to a tip of the actuator arm 103, a head slider 105 supported by the suspension 104 and including a read head and a write head, a voice coil motor (VCM) 106 that drives the actuator arm 103, and a head amplifier (not shown) that amplifies input signals to and output signals from the head. The head amplifier (HIC) is provided on the actuator arm 103 and connected to the printed circuit board (PCB) 200 via a flexible cable (FPC) 120. Providing the head amplifier (HIC) on the actuator arm 103 as described above enables an effective reduction in noise in head signals. However, the head amplifier (HIC) may be fixed to the HDA main body.

The perpendicular magnetic recording layer is formed on both sides of the DTR medium 55 as described above. On both sides, the servo zones are formed like circular arcs so as to coincide with the locus along which the head moves. Specifications for the magnetic recording medium satisfy an outer diameter, an inner diameter, and read/write properties which are adapted for the drive. The radius of the circular arc formed by the servo zone is given as the distance from the pivot to the magnetic head element.

Four main system LSIs are mounted on the printed circuit board (PCB) 200. The four main system LSIs include a disk controller (HDC) 210, a read/write channel IC 220, a MPU 230, and a motor driver IC 240.

The MPU 230 is a control section for a driving system and includes ROM, RAM, CPU, and a logic processing section which are required to implement a head positioning control system according to the present embodiment. The logic processing section is an arithmetic processing section composed of a hardware circuit to execute high-speed arithmetic processes. The firmware (FW) for the logic processing section is stored in ROM. MPU controls the drive in accordance with FW.

The disk controller (HDC) 210 is an interface section in the hard disk and exchanges information with an interface between the disk drive and a host system (for example, a personal computer), MPU, the read/write channel IC, and the motor driver IC to control the entire drive.

The read/write channel IC 220 is a head signal processing section composed of a circuit which switches a channel to the head amplifier (HIC) and which processes read/write signals.

The motor driver IC 240 is a driver section for the voice coil motor (VCM) 77 and the spindle motor 72. The motor driver IC 240 controls the spindle motor 72 to a given rotation speed and provides a VCM manipulation variable from MPU 230 to VCM 77 as a current value to drive a head moving mechanism.

While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 

1. A method of manufacturing a stamper used for manufacturing a magnetic recording medium comprising a magnetic pattern corresponding to servo areas comprising a preamble section, an address section and a burst section and data areas comprising discrete tracks, the method comprising: forming an additional resist pattern comprising alternating protrusions and recesses in the radial direction in the preamble section and/or address section, in the forming resist pattern corresponding to the servo areas comprising the preamble section, the address section and the burst section, and data areas comprising discrete tracks on a master plate; depositing a conductive film on the entire surface of the master plate and resist patterns; electroforming a metal layer; and peeling off the metal layer from the master plate.
 2. A method of claim 1, wherein the additional resist pattern comprises a redundant bit string comprising alternating “1” and “0” bits in the radial direction.
 3. A method of claim 1, wherein the additional resist pattern is used as an error correcting code.
 4. A method of claim 3, wherein the resist pattern corresponding to the error correcting code comprises a Hamming code.
 5. A method of claim 1, further comprising forming the resist pattern of the preamble section comprising the resist pattern divided by recesses in the radial direction.
 6. A method of claim 1, further comprising: forming the resist pattern in the circumferential direction separated from each other in the radial direction in a region of the master plate positioned on the outside of the outer periphery of the magnetic recording medium, the resist pattern comprising shapes similar to shapes of the discrete tracks.
 7. A method of claim 6, further comprising: removing a region of the metal layer peeled off from the master plate on the outside of the outer periphery of the magnetic recording medium after electroforming. 